1. Field of the Invention
The present invention relates to a semiconductor device, and more particularly to a guard ring structure for providing a noise shield.
2. Description of Related Art
In conventional semiconductor devices, a conductive region called a guard ring surrounds transistors formed on a semiconductor substrate. Connecting this guard ring to a ground potential shields the transistors from external noise input.
However, conventional semiconductor devices have the following problems.
The guard ring is formed as a conductive region wherein a high concentration of ions is diffused around the region on the semiconductor substrate where transistors are formed. For this reason, it is difficult to provide a resistance of zero entirely to the resistor portion of the guard ring and it is not possible to provide complete shielding from the effects of the external noise, especially in the case of high amplification transistors.
It is an object of the present invention to provide a semiconductor device comprising a guard ring that can effectively shield out external noise and resolve the problems with the abovementioned conventional art.
In order to resolve the abovementioned problems, the present invention is a semiconductor device comprising: a circuit region including transistors formed on the semiconductor substrate; a first guard ring of an ion diffused region formed around the abovementioned circuit region; a second guard ring of a high concentration ion diffused region formed around the abovementioned first guard ring with a prescribed gap therebetween; a first metal film pattern formed opposing to the abovementioned first guard ring with an insulating film interposed therebetween and that is connected to the first guard ring by a plurality of interlayer wires; a second metal film pattern formed opposing to the abovementioned second guard ring with the abovementioned insulating film interposed therebetween and that is connected to the second guard ring by a plurality of interlayer wires; a first metal wire connecting the abovementioned first metal film pattern to an external terminal to which a standard potential is provided; and a second metal wire connecting the abovementioned second metal film pattern to the abovementioned external terminal.
The present invention effects the following actions because the semiconductor device is constituted as above.
The first guard ring formed around the circuit region has the difference in potential within the ring eliminated and is connected to a standard potential by the first metal film pattern. Furthermore, the guard ring formed around the first guard ring has the difference in potential within the ring eliminated and is connected to the same standard potential as the first ring by the second metal film pattern.
External noise is thereby effectively shielded by the first and second guard rings and its influence on the circuit region can be eliminated.